Device for attaching a hub to a shaft, in particular a steering wheel hub to a steering column

ABSTRACT

A device for attaching a steering wheel hub to a steering wheel column, while simultaneously fixing a contact unit to the steering wheel, includes a fastener that has a head part engaging in the hub and a shank that engages partially in the hub and partially in the shaft. In a locked position, the fastener engages a recess in the contact unit to prevent the steering wheel hub from rotating relative to the stator of the contact unit. In an unlocked position, the fastener partially engages the hub, partially engages the column, and disengages from the recess in the contact unit to fixedly connect the hub to the column and allow the hub, and therefore the rotor of the contact unit, to rotate.

FIELD OF THE INVENTION

The invention relates generally to a device for fixing a hub to a shaft,and more particularly to a device for fixing a steering wheel hub to asteering column.

BACKGROUND OF THE INVENTION

It is known to fit steering wheels in motor vehicles on the steeringcolumns and to fix them on the same from above by means of a nut orscrew. A steering wheel fixing is also known from German Patent DE 44 15765 A where the steering wheel hub has a clamping element engaging inthe steering column. The steering column is provided with notched teethwhich are associated with corresponding teeth in the steering wheel hub.A clamping groove which is associated with a clamping element in thesteering wheel hub is provided in the area of the notched teeth in thesteering spindle for axially locking the steering wheel hub, and thusthe steering wheel, on the steering column. The clamping element therebyextends transversely to the steering column. With this type of fixing itis possible to mount an airbag unit on the steering wheel prior tofixing the steering wheel on the steering column since screwing up thenut from above is not necessary.

Contact units are known for transferring the electrical energy andsignals between stationary structural groups and the steering wheel ofthe motor vehicle. These contact units have a stator fixed on thesteering column and a rotor fixed on the steering wheel. A cable runsbetween the two and is wound up and down during rotation of the steeringwheel in dependence on the turning direction. The stator and rotor haveplug contacts by means of which they are connected with the steeringcolumn and steering wheel.

In practice, the contact unit is mounted at the same time as fitting thesteering wheel on the steering column. It is also known from practice topre-fit the rotor as well as the stator on the steering wheel. Fittingthe steering wheel on the steering column takes place in a definedposition, preferably when the vehicle wheels are aligned straight. Therotary position of the contact unit must correspond during fitting tothis defined position. It is therefore desirable that the contact unitprefitted on the steering wheel already has this position and that thisis maintained even during assembly. This has been possible up until nowonly very expensively by means of separate parts. The same also appliesto dismantling .

SUMMARY OF THE INVENTION

The object of the invention is to simplify the fixing of a hub on ashaft, and more particularly the steering wheel on the steering column,even in the case of a prefitted contact unit on the steering wheel.

With a device for fixing a hub on a shaft, more particularly a steeringwheel hub on a steering column, with a fixing device engagingtransversely into the shaft, wherein a screw is provided as the fixingmeans which has a head part engaging in the hub, and a shank whichengages partly in the hub and partly in the shaft according to theinvention with a contact unit provided on the steering wheel and havinga rotor fixed on the steering wheel and a stator fixed on the steeringcolumn, the stator has a section in which the screw engages in aposition of the steering wheel released from the steering column.

This device has the advantage that the screw released the section of thehead part projecting from the steering wheel can be used for fixing thecontact unit pre-fitted on the steering wheel. Thus the screw providedfor fitting the steering wheel on the steering column is usedadditionally for securing the contact unit against rotation. The addedadvantage is that this anti-rotational lock is produced simultaneouslyand automatically on undoing the screw from the steering column. Thus,neither an additional work step is required nor can the process oflocking be forgotten. This arrangement represents both a transportsecurity feature which prevents the stator from turning during transportof the steering wheel with the prefitted contact unit, and also anassembly aid which ensures that the steering wheel can only be fitted ina predetermined position, and more particularly in the straight linealignment of the wheels.

It is further expedient that on the edge of the stator there is a recesswhich has a size allowing the screw to be inserted with the head partinto the threaded guide of the steering wheel. The stator of the contactunit thereby preferably represents a hollow cylindrical part which isopen to the top and on whose edge a hole or incision is provided as arecess for the screw.

The screw can only be inserted into the threaded guide of the steeringwheel if the contact unit is turned so that the recess is aligned withthe threaded bore. By turning the screw, the contact unit is fixedwhereby the screw is only turned up to a depth where there is still nocontact with the steering column. The head part of the screw has such alength that in one position, where the steering wheel and steeringcolumn are fixedly connected together by the screw, the screw no longerengages in the recess, i.e. is no longer in engagement with the contactunit. The steering wheel and contact unit are thus unlocked and thesteering wheel, and with it the rotor, can be turned.

On the other hand the length of the head part can also be selected sothat the head part in the released position of the screw is both guidedin the hub and projects out of same.

It is expedient that the head part is provided with an external threadwhich is associated in the hub with a threaded guide, that the shank ofthe screw has adjoining the head part a first cylindrical section, thatthis is adjoined by a conical section for engagement in associatedsections of the hub and shaft and that the conical section is adjoinedby a second cylindrical section which is associated with a guide in thesteering wheel. The second cylindrical section has a smaller diameterthan the first cylindrical section.

The sections of the hub and/or shaft associated with the screw areformed as a circumferential recess or groove. Furthermore it isexpedient that the first cylindrical section has a larger diameter andthe second cylindrical section a smaller diameter than the recess orgroove provided on the shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained with reference to the embodimentsshown in the drawings in which:

FIG. 1 is a sectional view through a part of a steering wheel skeletonwith the contact unit in a locked position;

FIG. 2 is a plan view of the steering wheel skeleton of FIG. 1,partially in section;

FIG. 3 is a sectional view of the steering wheel skeleton of FIG. 1,with the contact unit in an unlocked position;

FIG. 4 is a plan view of the steering wheel skeleton according to FIG.3, partially in section;

FIG. 5 is a side view A of the steering wheel skeleton of FIG. 1,illustrating the fixing means; and

FIGS. 6A-D are sectional views of the fixing means of the steering wheelskeleton taken along lines 6--6 illustrating four different embodiments.

FIG. 1 shows a part of the skeleton of a steering wheel 1 to which arotor 2 of a contact unit is connected. The steering column is not shownin the figure. The rotor 2 is associated with a stator 3 which is guidedin a ring groove 4 in the rotor 2. This guide allows the prefitting ofalso the stator on the steering wheel so that the steering wheel can besupplied to the vehicle manufacturer with the rotor and stator, i.e. asa complete contact unit.

In order to fix the steering wheel 1 on the steering column, which isnot shown in FIGS. 1 to 4, a screw 5 is provided which lies transverselyrelative to the steering column and which, in a released positionremoved from the steering column, engages in a recess 6 (FIG. 3) on theedge 7 of the stator of the contact unit. These component parts are alsoshown in the view of FIG. 5. The screw 5 has a head part 8 provided withan external thread wherein the recess 6 has on the edge 7 of the contactunit a size which allows the screw 5 to be inserted with the head part 8into a threaded guide 9 of the steering wheel 1. The screw furthermorehas a shank which, after fixing the steering wheel on the steeringcolumn, engages by part of its circumference in the steering wheel hub10 and by another part in the steering column 11 (FIGS. 6A to 6D). Theshank of the screw 5 has adjoining the head part 8 a first cylindricalsection 12. This is adjoined by a conical section 13, which is adjoinedby a second cylindrical section 14 having a smaller diameter than thefirst cylindrical section 12.

FIGS. 1 and 2 show the screw 5 in the released position where the headpart 8 engages in the recess 6 (FIG. 3). The stator is thus securedagainst turning during transport of the steering wheel. Also, in thisposition the head part 8 is still guided in the threaded guide 9 of thesteering wheel 1 so that the head part 8 remains in the recess 6independently of the position of the steering wheel during transport.Furthermore, during assembly of the steering wheel on the steeringcolumn 11 a predetermined position of the rotor relative to the statoris ensured.

During assembly of the steering wheel on the steering column the screw 5is tightened. The head part 8 is thereby moved inwards over the edge 7so that the anti-rotation lock is lifted. The rotor can thereby, duringrotation of the steering wheel, rotate relative to the stator 3 which isfixed on the steering column 11. In the fitted position of the steeringwheel shown in FIGS. 3 and 4, the conical section 13 of the screw 5engages, in the manner shown in FIG. 6, in the steering wheel hub 10 andsteering wheel column 11. The second cylindrical section 14 engages in acylindrical recess 15 whereby the screw 5 is additionally guided.

The connection between the steering wheel hub 10 and the steering column11 is also shown in FIGS. 6A-D. With the embodiments of FIGS. 6A and 6Bthe steering column 11 has a recess 17 which is opposite a recess 18 inthe steering wheel hub 10. When screwing in the screw 5 its conicalsection 13 engages between the two recesses. The recess 17 can have botha round cross-section, as shown in FIG. 6, and also a polygonalcross-section, as shown in FIG. 6B. In the embodiments of FIGS. 6C and6D the steering column 11 has a circumferential groove 16 which isassociated with a groove 18 in the steering wheel hub 10. The conicalsection 13 engages on one side in this groove and also engages in thegroove 18. The circumferential groove 16 can have both a roundcross-section (FIG. 6C) and a polygonal cross-section (FIG. 6D).

What is claimed is:
 1. An assembly comprising:a steering wheel having asteering wheel hub, the hub having a shaft opening for receiving a shaftof a steering column; fixing means engaging transversely into the shaftopening wherein a screw is provided as the fixing means and has a headpart engaging in the hub and a shank which engages partly into the shaftopening; and a contact unit having a stator and a rotor provided on thesteering wheel with the rotor fixed on the steering wheel hub, the rotorrotates relative to the stator when the screw engages into the shaftopening, and the stator having a section in which the screw engages toprevent the rotation of the rotor relative to the stator when the screwis in a position released from the shaft opening.
 2. The assemblyaccording to claim 1 wherein the stator comprises an edge provided witha recess which has a size which allows the screw to be inserted with thehead part into a threaded guide of the steering wheel hub.
 3. Theassembly according to claim 1 wherein the stator comprises a hollowcylindrical part and a hole is provided on an edge of the stator as arecess for the screw.
 4. The assembly according to claim 1 wherein thehead part has such a length that when the screw is loosened from thesteering column, the head part is both guided in the hub and projectsout of the hub.
 5. The assembly according to claim 2 wherein the headpart is provided with an external thread which is associated in the hubwith the threaded guide, and wherein the shank of the screw comprises:afirst cylindrical section, adjoining the head part and having adiameter, a conical section, adjoining the first cylindrical section,for engagement in associated sections of the hub and the column, and asecond cylindrical section, adjoining the conical section and having adiameter, which is associated with a guide in the steering wheel hub. 6.The assembly according to claim 5 wherein the diameter of the secondcylindrical section is smaller than the diameter of the firstcylindrical section.
 7. The assembly according claim 6 wherein the hubcomprises a recess and the column comprises a recess opposite the recessin the hub, and wherein the screw is adapted to be received between therecess provided in the hub and the recess provided in the column.
 8. Theassembly according claim 7 wherein the diameter of the first cylindricalsection is larger, and the diameter of the second cylindrical section issmaller, than a diameter of the recess provided in the column.
 9. Theassembly according to claim 7 wherein the recess provided in the columnhas a round cross-section.
 10. The assembly according to claim 7 whereinthe recess provided in the column has a polygonal cross-section.
 11. Theassembly according claim 6 wherein the hub comprises a recess and thecolumn comprises a circumferential groove opposite the recess in thehub, and wherein the screw is adapted to be received between the recessprovided in the hub and the circumferential groove provided in thecolumn.
 12. The assembly according to claim 11 wherein the diameter ofthe first cylindrical section is larger, and the diameter of the secondcylindrical section is smaller, than a diameter of the circumferentialgroove provided in the column.
 13. The assembly according to claim 11wherein the recess provided in the column has a round cross-section. 14.The assembly according to claim 11 wherein the recess provided in thecolumn has a polygonal cross-section.
 15. A steering wheel comprising:asteering wheel hub; a steering wheel column; a contact unit having arotor coupled to the steering wheel hub and a stator having a recess;and a fastener aligned with the recess, wherein, in a locked position,the fastener engages the recess to prevent the steering wheel hub fromrotating relative to the stator, and wherein, in an unlocked position,the fastener partially engages the hub, partially engages the column,and disengages from the recess to fixedly connect the hub to the columnand allow the hub, and therefore the rotor, to rotate.
 16. The steeringwheel according to claim 15 wherein the fastener comprises:an externallythreaded head section, and a shank section adjacent to the head section,wherein the shank section includes a first cylindrical section, adjacentthe head section and having a diameter, a conical section, adjacent thefirst cylindrical section, and a second cylindrical section, adjacentthe conical section and having a diameter.
 17. The steering wheelaccording to claim 16 wherein the diameter of the second cylindricalsection is smaller than the diameter of the first cylindrical section.18. The steering wheel according claim 17 wherein the hub comprises arecess and the column comprises a recess opposite the recess in thehub,wherein the screw is adapted to be received between the recessprovided in the hub and the recess provided in the column, and whereinthe diameter of the first cylindrical section is larger, and thediameter of the second cylindrical section is smaller, than a diameterof the recess provided in the column.
 19. The steering wheel accordingto claim 18 wherein the recess provided in the column has a roundcross-section.
 20. The steering wheel according to claim 18 wherein therecess provided in the column has a polygonal cross-section.
 21. Thesteering wheel according claim 17 wherein the hub comprises a recess andthe column comprises a circumferential groove opposite the recess in thehub,wherein the screw is adapted to be received between the recessprovided in the hub and the circumferential groove provided in thecolumn, and wherein the diameter of the first cylindrical section islarger, and the diameter of the second cylindrical section is smaller,than a diameter of the circumferential groove provided in the column.22. The steering wheel according to claim 21 wherein the recess providedin the column has a round cross-section.
 23. The steering wheelaccording to claim 21 wherein the recess provided in the column has apolygonal cross-section.